Ionic liquids

ABSTRACT

The invention relates to an ionic liquid composition and a method for preparing the ionic liquid. The ionic liquid comprises a cation containing the Formula I, as herein disclosed, and wherein: n is 2, R 1  is selected from the group consisting of: H, C 1 -C 12  alkyl, aryl or together with R 2  may form a heterocyclic ring, and R 2  is selected from the group consisting of: H, C 1 -C 12  alkyl, aryl or together with R 1  may form a heterocyclic ring, and R 3  is selected from the group consisting of hydrogen and C 1 -C 12  alkyl, and wherein R 1  and R 2  are not simultaneously selected from hydrogen.

The present invention relates to heterocyclic compounds that are usefulas ionic liquids. This application claims benefit of priority fromProvisional Application No. 60/941,406, filed Jun. 1, 2007. Thisapplication hereby incorporates by reference Provisional Application No.60/941,406 in its entirety.

FIELD OF THE INVENTION Background

An ionic liquid is a liquid that contains essentially only ions, i.e.molten salts, although some ionic liquids are in a dynamic equilibriumwherein the majority of the liquid is made up of ionic species ratherthan molecular species. As used herein, the term “ionic liquids” refersto liquids composed of ions. In one embodiment, the term “ionic liquids”refers to liquids composed of ions which are liquid at or below about100° C.

Ionic liquids generally consist of salts of organic cations. The organiccations are generally bulky and asymmetric such asN-methyl-N-alkylpyrrolidinium, N-alkylpyridinium,1-alkyl-3-alkylimidazolium, and tetraalkylammonium ions. A number ofdifferent anions may be employed, from halides to inorganic anions suchas hexafluorophosphate and tetrafluoroborate and to large organic anionslike bis(trifluoromethanesulfonyl)imide, trifluoroacetate ortoluene-4-sulfonate. For instance, U.S. Pat. No. 7,157,588 B2 teachescompositions based on N-substituted pyrrolidinones having a pendantammonium cation separated from the pyrrolidone ring by a variable lengthalkyl spacer. WO 2006/136529 teaches pyrazolium alkylsulfates and amethod for their production.

The object of the present invention is to provide novel ionic liquidcompositions.

DESCRIPTION OF THE INVENTION

According to the present invention there is provided an ionic liquidcomprising a cation according to Formula I:—

wherein:n is 2,R¹ is selected from the group consisting of H, C₁-C₁₂ alkyl, aryl ortogether with R² may form a heterocyclic ring, andR² is selected from the group consisting of: H, C₁-C₁₂ alkyl, aryl ortogether with R¹ may form a heterocyclic ring, andR³ is selected from the group consisting of hydrogen and C₁-C₁₂ alkyl,wherein R¹ and R² are not simultaneously selected from hydrogen; andwherein the ionic liquid additionally comprises dicyanamide.

In a preferred embodiment, R³ is hydrogen.

As used herein, the term “alkyl” means a branched or unbranched, cyclicor acyclic, saturated or unsaturated (i.e. alkenyl or alkynyl)hydrocarbyl radical which may be substituted or unsubstituted. Wherecyclic, the alkyl group is preferably C₃ to C₁₂, more preferably C₅ toC₁₀, more preferably C₅, C₆ or C₇. Where acyclic, the alkyl group ispreferably C₁ to C₁₀, more preferably C₁ to C₆, more preferably methyl,ethyl, propyl (n-propyl or isopropyl), butyl (n-butyl, isobutyl ortertiary-butyl) or pentyl (including n-pentyl and iso-pentyl), morepreferably methyl. It will be appreciated therefore that the term“alkyl” as used herein includes alkyl (branched or unbranched), alkenyl(branched or unbranched), alkynyl (branched or unbranched), cycloalkyl,cycloalkenyl and cycloalkynyl.

An alkyl group may be substituted with one or more substituents whereinpossible substituents include alkyl; aryl; heteroaryl; arylalkyl (e.g.substituted and unsubstituted benzyl, including alkylbenzyl); halogenatoms and halogen-containing groups such as haloalkyl (e.g.trifluoromethyl) or haloaryl (e.g. chlorophenyl); alcohols (e.g.hydroxy, hydroxyalkyl, hydroxyaryl, (aryl)(hydroxy)alkyl); ethers (e.g.alkoxy, aryloxy, alkoxyalkyl, aryloxyalkyl, alkoxyaryl, aryloxyaryl) andcarboxyl (e.g. carboxaldehyde, alkyl- or aryl-carbonyl, carboxy,carboxyalkyl or carboxyaryl), amide and nitrile.

Subject to the constraints of formula I above, R¹ and R² may be the sameor different and in one embodiment are different.

R¹ and R² may together form a heterocyclic ring comprising at least 2carbon atoms and one nitrogen atom.

As used herein, a “heterocyclic ring” refers to a monocyclic, saturatedor partially unsaturated, heterocyclic radical in which the ringcontains at least 3 members, preferably 3-12 members, more preferably 5or 6 members, of which one member is a N atom and at least two of theother members are C atoms. Preferably the heterocyclic ring isunsubstituted. By way of non-limiting example, suitable N-heterocyclylgroups include aziridinyl, azetidinyl, pyrrolidinyl, piperidyl,azepanyl, azocanyl, azonanyl, azecanyl, azacycloundecanyl andazacyclododecanyl.

As used herein, the term “aryl” means a carbocyclic aromatic group, suchas phenyl or naphthyl (preferably phenyl).

The aryl group may be substituted with one or more substituents whereinpossible substituents include alkyl; aryl; heteroaryl; arylalkyl (e.g.substituted and unsubstituted benzyl, including alkylbenzyl); halogenatoms and halogen-containing groups such as haloalkyl (e.g.trifluoromethyl) or haloaryl (e.g. chlorophenyl); alcohols (e.g.hydroxy, hydroxyalkyl, hydroxyaryl, (aryl)(hydroxy)alkyl); ethers (e.g.alkoxy, aryloxy, alkoxyalkyl, aryloxyalkyl, alkoxyaryl, aryloxyaryl) andcarboxyl (e.g. carboxaldehyde, alkyl- or aryl-carbonyl, carboxy,carboxyalkyl or carboxyaryl), amide and nitrile. Preferably the arylgroup is unsubstituted.

As used herein, the term “heteroaryl” means an aromatic group containingone or more heteroatom(s) preferably selected from N, O and S, such aspyridyl, pyrrolyl, quinolinyl, furanyl, thienyl, oxadiazolyl,thiadiazolyl, thiazolyl, oxazolyl, isoxazolyl, pyrazolyl, triazolyl,imidazolyl, pyrimidinyl, indolyl, pyrazinyl or indazolyl.

As used herein, the term “halogen” means a fluorine, chlorine, bromineor iodine radical.

In one embodiment, neither R¹ nor R² is selected from hydrogen.

In one embodiment, both R¹ and R² are optionally substituted C₁-C₁₂alkyl groups. Preferably, R¹ is an optionally substituted C₁-C₆ alkylgroup and/or R² is an optionally substituted C₁-C₆ alkyl group.Preferably the R¹ and R² alkyl groups are unsubstituted. Preferably R¹is an unsubstituted butyl group. Preferably R² is a methyl group.Preferably the ionic liquid cation is of formula Ia or Ib, i.e.1-butyl-1-methylazepanium or 1-butyl-1,3-dimethylpiperidinium,respectively:

In a further embodiment, one of R¹ and R² is an optionally substitutedC₁-C₁₂ alkyl group and the other is an optionally substituted arylgroup. Preferably the optionally substituted alkyl group is anoptionally substituted C₁-C₆ alkyl group. Preferably the alkyl group isunsubstituted. Preferably the aryl group is unsubstituted.

In a further embodiment, both R¹ and R² are optionally substituted arylgroups. Preferably the aryl groups are unsubstituted.

In a further embodiment, R¹ and R² together form a heterocyclic ring.Preferably the heterocyclic ring is unsaturated. Preferably theheterocyclic ring is an unsaturated ring with 5 or 6 members. In thisembodiment, preferably the ionic liquid cation is of formula Ic,6-azonia-spiro[5,6]dodecane:

In a further embodiment, the ionic liquid comprises one or moredifferent cations all represented by Formula I.

In a further embodiment, the ionic liquid comprises one or moredifferent cations all represented by Formula I and one or more furthercations selected from the group consisting of imidazolium, pyrazolium,oxazolium, thiazolium, triazolium, pyridinium, pyridazinium,pyrimidinium, phosphonium and pyrazinium, wherein the further cation oreach of said further cation(s) is substituted with a substituent groupselected from C₁-C₁₂ alkyl or aryl as defined herein, preferably C₁-C₁₂alkyl.

The ionic liquid according to formula I comprises an anion, X⁻,preferably selected from the group consisting of:bis(trifluoromethylsulphonyl)imide; dicyanamide; hexahalophosphates(preferably hexafluorophosphate or hexachlorophosphate);tetrahaloborates (preferably tetrafluoroborate or tetrachloroborate);halides; nitrates; sulfates; phosphates; carbonates; sulfonates;carboxylates and silicates.

The sulfates may be selected from the group consisting of sulfate,hydrogen sulfate, alkyl or aryl sulfate, alkyl or aryl sulfonates,trifluoromethanesulfonate, and toluene-4-sulfonate, alkyl or aryloxoanion sulfates. Preferably the oxoanion sulfates are selected frompersulfate (SO₅ ²⁻), sulfite (SO₃ ²⁻), hyposulfite (SO₂ ²⁻),peroxydisulfite (S₂O₈ ²⁻).

The phosphates may be selected from the groups consisting of: phosphate;hydrogen phosphate; dihydrogen phosphate, alkyl or aryl phosphate, alkylor aryl phosphonates, alkyl or aryl phosphinates, other oxoanionphosphates and metaphosphate.

The carbonates may be selected from the group consisting of carbonateand hydrogen carbonate, alkyl or aryl carbonates and other oxoanioncarbonates.

The carboxylates may be selected from the group consisting of:alkylcarboxylates; arylcarboxylates and ethylenediaminetetraacetate.

As used herein, the term “alkylcarboxylates” refers to alkyl compoundswith one or more carboxylate groups, preferably one, two or threecarboxylate groups. Alkylcarboxylates include formate; acetate,propanoate, butanoate, pentanoate, hexanoate, heptanoate, octanoate,nonanoate, decanoate, oxalate; succinate; crotonate; fumarate. The term“alkylcarboxylates”, as used herein, further includes carboxylateswherein the alkyl group is substituted with the substituent groupsreferred to herein and therefore further includes glycolate; lactate;tartrate; hydrogen tartrate; malate; citrate; trifluoroacetate;pentafluoropropanoate; heptafluorobutanoate; mandelate; andphenylacetate

As used herein, the term “arylcarboxylates” refers to aryl compoundswith one or more pendant carboxylate groups, preferably one, two orthree carboxylate groups. Arylcarboxylates include benzoate;benezenedicarboxylate; benzenetricarboxylate; benzenetetracarboxylate;chlorobenzoate; fluorobenzoate; pentachlorobenzoate; pentafluorobenzoateand salicylate.

Preferably X⁻ is dicyanamide or bis(trifluoromethanesulfonyl)imide.

Preferably, the ionic liquid comprising the cation of formula I and theanion X⁻ is selected from the group consisting of1-butyl-1-methyl-azepanium bis(trifluoromethanesulfonyl)imide,1-butyl-1-methyl-azepanium dicyanamide, 6-azonia-spiro[5,6]dodecanebis(trifluoromethanesulfonyl)imide, 6-azonia-spiro[5,6]dodecanedicyanamide, 1-butyl-1,3-dimethylpiperidiniumbis(trifluoromethanesulfonyl)imide and 1-butyl-1,3-dimethylpiperidiniumdicyanamide.

According to a further aspect of the present invention there is provideda method for the preparation of an ionic liquid according to formula Iwherein the method comprises at least one N-substitution of the compoundof formula II:

wherein:

-   n is 1 or 2,-   R³ is selected from the group consisting of hydrogen and C₁-C₁₂    alkyl, and wherein when n is 1, R³ is C₁-C₁₂ alkyl, preferably    methyl.

In a preferred embodiment, if n=2, then R³ is hydrogen.

As used herein, the step of N-substitution is an N-alkylation orN-arylation step and comprises contacting an N-substitution agent (i.e.an N-alkylating or N-arylating agent) with the compound of Formula II.Such synthetic procedures are well known in the art and may be carriedout using any method known to the skilled person. In a preferredembodiment, the N-substitution step is an N-alkylation. A non-limitingexample of the N-alkylation of azepane is described in the Journal ofOrganic Chemistry, Vol. 60, No. 26, 1995, 8371-8374. The N-substitutionsteps are described herein below with reference to N-alkylation althoughit will be appreciated that corresponding N-arylation steps areavailable to the skilled person.

The or each N-alkylation step(s) may be carried out with any C₁-C₁₂alkylating reagent that is capable of quaternarising the amine nitrogenof formula II. Preferably the or each N-alkylation step is carried outusing C₁-C₁₂ alkylating agent(s) selected from the group consisting ofC₁-C₁₂ alkylating agents (e.g. alkyl halides, alkyl sulfonates or alkylsulfates). The corresponding N-arylation reactions can be carried outusing aryl sulfonates or aryl sulfates.

Preferably, the or each N-substitution reaction(s) may be carried out inan inert solvent, such as acetonitrile, acetone, methanol ordichloromethane.

In one embodiment, a single N-substitution step is carried out. Theionic liquid produced using the method of this embodiment has theformula described by formula I, wherein R¹ or R² is hydrogen.

In a further embodiment, two N-substitution steps are carried out. Theionic liquid produced using the method of this embodiment has theformula described by formula I, wherein neither R¹ nor R² is hydrogen.

In the embodiment comprising two N-substitution steps, bothN-substitution steps may be carried out using the same N-substitutionagent. Preferably, different N-substitution agents are used for eachN-substitution step.

The two N-substitution steps may be carried out sequentially orsimultaneously and are preferentially carried out sequentially.

Preferably, the two N-substitution steps are carried out sequentiallywith different N-substitution agents. Preferably, the firstN-substitution step is carried out with the N-alkylating agent butylbromide. Preferably the second N-substitution step is carried out withthe N-alkylating agent methyl iodide.

Preferentially the single or first N-substitution step is carried out ata temperature below about 100° C., more preferably below about 75° C.,more preferably below about 50° C., more preferably below about 20° C.

In the embodiment where there are two N-substitution steps, preferablythe two N-substitution steps are carried out sequentially. The secondN-substitution step is carried out at a temperature below about 100° C.,more preferably below about 75° C., more preferably below about 50° C.,more preferably below about 20° C. Preferably, after the reagents areadded the reaction mixture is warmed to a temperature from about 0° C.to about 100° C., more preferably from about 0° C. to about 75° C., morepreferably from about 0° C. to about 50° C., more preferably about roomtemperature.

The anion component of the single or second N-substitution step may formthe ionic liquid anion, X⁻. Preferably the anion component of the singleor second N-substitution is selected from the group consisting ofhalides, sulfonates and sulfates.

In an alternative embodiment, the method may additionally comprise thestep of anion exchange of the N-substituted salt product. Prior to theanion exchange, excess N-substitution agent may be removed, for example,by evaporation. In addition, the N-substituted salt product may bewashed with a solvent prior to the anion exchange step.

The anion exchange step comprises contacting the N-substituted solutionproduct with an ion exchange agent, optionally in an inert atmosphere.Preferably the anion exchange step is carried out at a temperature offrom about 0° C. to about 100° C., more preferably from about 0° C. toabout 75° C., more preferably from about 0° C. to about 50° C., morepreferably about room temperature. Preferably the N-substituted solutionproduct and the ion exchange agent are contacted and stirred for severalhours (e.g. from about 0.5 to about 24 hours, preferably from about 1 toabout 15 hours, more preferably from about 4 to about 12 hours). The ionexchange agent comprises an X⁻ anion as defined above but which isdifferent to the anion component of the single or second N-substitutionstep present in the product obtained from the single or secondN-substitution step.

Preferably the ion exchange agent is a metal salt of the anion X⁻,defined previously. Preferably, the metal is an alkali metal or analkaline earth metal.

The optional anion exchange step is typically conducted in solution.Solvents use in the anion exchange reaction should be inert to thereactants and the products and include methanol, ethanol, acetone,acetonitrile and water, preferably water. In one embodiment, the choiceof the appropriate solvent, or mixture of solvents, that will allow forseparation of the composition comprising the desired anion from thecomposition comprising the less desired anion is well known in the artand is exemplified in example 1. The composition comprising the desiredanion can then be recovered using a suitable technique such asevaporation or the reactant solvent, decantation, re-crystallisationand/or filtration.

In an alternative embodiment, the anion exchange agent may be contactedwith the N-substituted salt product and mixed in a solvent for a periodof time, i.e. more than about 5 hours. The composition comprising thedesired anion can then be recovered using a suitable technique such asevaporation or the reactant solvent, decantation, re-crystallisationand/or filtration.

Preferably formula II represents a compound selected from the groupconsisting of azepane and 3-methylpiperidine.

In one embodiment, formula II may represent azepane. The azepanerepresented by formula II may be a by-product of the manufacture of1,6-hexanediamine. In a further embodiment, formula II may represent3-methylpiperidine. The 3-methylpiperidine represented by formula II maybe a by-product of the manufacture of 2-methyl-1,5-pentanediamine. Inthese by-product embodiments, the 1,6-hexanediamine may be produced bythe hydrogenation of hexanedinitrile and the 2-methyl-1,5-pentanediaminemay be produced by the hydrogenation of 2-methylpentanedinitrile.

In this embodiment, the hydrogenation reactions are preferably carriedout in the presence of hydrogen gas and a catalyst, e.g. an ironcatalyst or a Raney cobalt catalyst. The hydrogenation reactions arepreferably carried out at an elevated temperature (e.g. from about 30°C. to about 500° C., preferably from about 50° C. to about 350° C.,preferably from about 80° C. to about 200° C., preferably from about 80°C. to about 150° C.). The hydrogenation reactions are preferably carriedout at elevated pressure (e.g. from about 400 psig to about 8000 psig,preferably from about 1000 psig to about 6000 psig, preferably about1500 psig to about 5000 psig, preferably from about 3000 psig to about5000 psig). Preferably, when using an iron catalyst, the hydrogentationreaction is carried out at a temperature of from 80° C. to about 200°C., preferably about 140° C. and/or a pressure of from about 1500 psigto about 5000 psig, preferably about 4500 psig. Preferably, when using aRaney cobalt catalyst, the hydrogentation reaction is carried out at atemperature of from 80° C. to about 150° C., preferably about 115° C.and/or a pressure of from about 400 psig to about 2500 psig, preferablyabout 800 psig. Preferably the compound of formula II is separated fromthe product mixture, i.e. the crude 1,6-hexanediamine or2-methyl-1,5-pentanediamine, by distillation at reduced pressure andelevated temperature.

According to a further aspect of the present invention there is providedthe use of an ionic liquid of the present invention in a chemicalmethod.

As used herein, the term “chemical method” refers to any method used inchemistry. Chemical methods of the present invention includeseparations, extractions and syntheses, and encompass for instance theuse of ionic liquids as solvents and as catalysts, biocatalysts, and inenzyme processes. The chemical method of the present invention furtherencompass the use of ionic liquids in heat storage applications, fuelcells, battery fluids, polymerisation, catalysis, protein purification,metal deposition, and as lubricants and surfactants.

According to a chemical method as used herein, the ionic liquids of theapplicant's disclosures relate also to their cathodic stability whenused as an electrolyte, characterized by a higher decomposition voltagethan aqueous electrolytes for example. This higher decomposition voltageis implied by the measure of their “electrochemical window.” Theelectrochemical window of a substance is a voltage range between whichthe substance does not become oxidized nor reduced.

Electrochemical window is measured using cyclic voltammetry methods,methods commonly known to the skilled practioner. In brief, the cyclicvoltammetry analysis conducted by varying the voltage between twoelectrodes through an electrolyte and measuring the change in currentwith respect to change in voltage. The resulting cyclic voltammogram isrepresented in a current (ampere) versus voltage applied (volt) plot.The ionic liquids reported herein, according to Formula Ia and Ibpreviously, when used with the bis(trifluoromethylsulphonyl)amide anionand measured on glass calomel (GC) against Ag/Ag+ reference electrodeexhibit a window of stability, being neither oxidized nor reduced from−3.5 volts to +3.0 volts.

As a chemical method for the ILs herein disclosed, the electro-oxidationof depolymerization products from nylon 6 or nylon 66 is provided.According to the teachings of U.S. Pat. No. 5,468,900 to McKinney etal., herein incorporated in their entirety, the conversion of nylon 6and/or nylon 6,6 to adipic acid through at least an electrochemicalmeans for oxidation is provided. Mckinney et al. exemplify a variety ofoxidation techniques from which 6-alkylamidohexanoic acid, to yieldadipic acid, can be carried out by a variety of oxidation techniques,e.g. using air, oxygen or hydrogen peroxide. Alternatively the oxidationcan be carried out in a subsequent step after the depolymerization iscomplete. The oxidation may also be carried out electro-chemically. Thedepolymerization products may be isolated from the depolymerizationreaction mixture and redissolved in a suitable solvent containing anelectrolyte prior to electrolysis. Alternatively, an electrolyte may beadded directly to the polymerization reaction mixture, avoiding the needfor isolating the depolymerization products. Optionally, an oxidationcatalyst may be added to the solution. The mixture being oxidized may bechecked periodically and the process continued until substantial amountsof adipic acid have been produced. Alternatively, the oxidation may becontinued until the theoretical number of coulombs have been passed. Atthat point the solvent can be removed and the adipic acid recovered fromthe mixture containing the other reaction product, alkylamide, bycrystallization or by other means.

The Applicants believe that a chemical method employing the ionicliquids disclosed herein and having a high cathodic stability when usedas an electrolyte and solvent may be used to electrochemically oxidizethe same materials as disclosed by Mckinney et al. The chemical methodproposes to convert nylon 6 and/or nylon 6,6 to adipic acid monomer bydepolymerization with an aliphatic monocarboxylic acid to formalkylamides followed by an electrochemical oxidation of the alkylamidesto adipic acid and performed using only the ionic liquid as a solventand electrolyte, with an option to add mineral acids, such as: sulfuricacid and phosphoric acid.

The Applicants believe that the electrochemical oxidation of6-acetamidohexanoic acid, the primary acetylation product of nylon 6 canbe carried using substantially an ionic liquid solvent as theelectrolyte. Optionally, an acidic co-solvent, sulfuric acid, may bepresent to add conductivity of the resulting solution. Following theteachings of Mckinney et al., the 6-acetamidohexanoic acid is placed ina single compartment electrolytic cell fitted with parallel platinumfoil electrodes, one inch apart and is charged with 7 grams6-acetamidohexanoic acid and 75 ml of the ionic liquid and 2 ml ofconcentrated sulfuric acid. The contents of the cell are stirred with amagnetic stirrer bar during the electrolysis. The electrodes areconnected to an electrical circuit containing a suitable direct currentpower supply, an ammeter and a coulometer. The electrolysis is conductedat a current of 480 milliamperes at a cell voltage of 2.9 volts for asufficient time to accumulate 8074 coulombs. At the end of such anexperimental run a sample examined by GC/MS would reveal the majorcomponents to be 6-acetamidohexanoic acid, adipic acid and 5-formylvalerie acid. It is believed that the product mixture would be found tocontain adipic acid and 6-acetamidohexanoic acid (as determined byquantitative analysis by calibrated liquid chromatography) at about a50% conversion of 6-acetamidohexanoic acid to yield 70% adipic acid on amolar basis about a 70.% current efficiency.

In a manner similar to that above, it is expected that theelectrochemical oxidation of N,N′-hexamethylene bisacetamide, theacetylation product of nylon 6,6. The same electrolysis apparatus asemployed above is used. The cell is charged with 4 grams ofN,N′-hexamethylene bisacetamide and 75 ml of the ionic liquid and 2 mlof concentrated sulfuric acid. The electrolysis is conducted at acurrent of 480 millamperes at a cell voltage of 3.1 volts for asufficient time to accumulate 8050 coulombs. It is expected that at theend of the run a sample examined by GC/MS would reveal the majorcomponents to be N,N′-hexamethylene bisacetamide, 6-acetamidohexanoicacid, adipic acid, 5-formyl valeric acid and 6-acetamidocaproaldehyde.At a 60% conversion of N,N′-hexamethylene bisacetamide, a 13% yield to6-acetamidohexanoic acid and 18% yield to adipic acid on a molar basisis expected.

According to a further aspect of the present invention there is providedthe use of azepane and 3-methylpiperidine as precursors in the formationof ionic liquids.

The invention is further illustrated by the following examples. It willbe appreciated that the examples are for illustrative purposes only andare not intended to limit the invention as described above. Modificationof detail may be made without departing from the scope of the invention.

EXAMPLES Example 1

The first N-substitution of azepane was carried out using butyl bromideas an N-alkylating agent to form 1-butylazepane. An equimolar amount ofbutyl bromide was added dropwise to a solution of azepane in methanolkeeping the temperature at 20° C. by an ice-water bath. The mixture washydrolyzed with potassium carbonate, extracted with ether, and driedover Na₂SO₄. The solution was fractionally distilled at reduced pressureand the fraction with bp 195° C. was collected. ¹H-NMR (300 MHz, CDCl₃)δ 0.90 (t, 3H), 1.28 (sextet, 2H), 1.42 (m, 2H), 1.60 (broad m, 8H),2.42 (m, 2H), 2.60 (m, 4H).

Following this, a second N-substitution was carried out on the1-butylazepane using methyl iodide as an N-alkylating agent to form1-butyl-1-methylazipanium iodide. A slight excess of methyl iodide wasadded dropwise to 1-butylazepane in dichloromethane keeping thetemperature below 20° C. by an ice-water bath. The reaction mixture wasthen allowed to warm to room temperature and stirred until completeconversion of amine (as determined using ¹H nmr). Diethyl ether was thenadded to the reaction mixture and the white precipitate filtered, washedwith ether and dried in air. The white solid 1-butyl-1-methylazipiniumiodide melted at 214° C. ¹H-NMR (300 MHz, CDCl₃) δ 1.00 (t, 3H), 1.40(m, 2H), 1.78 (m, 6H), 1.90 (m, 4H), 3.02 (s, 3H), 3.30 (m, 2H), 3.40(m, 4H).

A slight excess of lithium bis[(trifluoromethyl)sulfonyl]imide dissolvedin water was added to an aqueous solution of 1-butyl-1-methylazipiniumiodide and stirred at room temperature for approximately 5 hours. Thereaction mixture was transferred to a separating funnel and the heavylayer washed several times with water. The addition of a small amount ofdichloromethane aided the separation of the aqueous and organic layer.The heavy organic layer was then evaporated to dryness leaving a paleyellow liquid, 1-butyl-1-methylazipiniumbis[(trifluoromethyl)sulfonyl]imide. ES/MS 170 (Cation C₁₁H₂₄N), −280(Anion C₂F₆NS₂O₄).

Example 2

1-butyl-1-methylazipanium iodide was formed according to example 1.

A slight excess of silver dicyanamide (freshly prepared from AgO andNaN(CN)₂) was added to an aqueous solution of 1-butyl-1-methylazipiniumiodide and stirred at room temperature for several hours. The reactionmixture was filtered and the filtrate evaporated to dryness leaving aclear liquid, 1-butyl-1-methylazipinium dicyanamide. ESIMS 170 (CationC₁₁H₂₄N), −66 (Anion C₂N₃).

Example 3

The first N-substitution of 3-methylpiperidine was carried out usingbutyl bromide as an N-alkylating agent to form1-butyl-3-methylpiperidine. An equimolar amount of butyl bromide wasadded dropwise to a solution of 3-methylpiperidine in methanol keepingthe temperature at 20° C. by an ice-water bath. The mixture washydrolyzed with potassium carbonate, extracted with ether, and driedover Na₂SO₄. The solution was fractionally distilled at reduced pressureand the fraction with bp 195° C. was collected. ¹H-NMR (300 MHz, CDCl₃)δ 0.82 (d, 3H), 0.90 (t, 3H), 1.30 (m, 2H), 1.48 (m, 2H), 1.65 (m, 5H),2.24 (m, 2H), 2.82 (m, 4H).

Following this, a second N-substitution was carried out on the1-butyl-3-methylpiperidine using methyl iodide as an N-alkylating agentto form 1-butyl-1-methyl-3-methylpiperidinium iodide. A slight excess ofmethyl iodide was added dropwise to 1-butyl-3-methylpiperidine indichloromethane keeping the temperature below 20° C. by an ice-waterbath. The reaction mixture was then allowed to warm to room temperatureand stirred until complete conversion of amine (as determined using ¹Hnmr). Diethyl ether was then added to the reaction mixture and the whiteprecipitate filtered, washed with ether and dried in air. The whitesolid form 1-butyl-1-methyl-3-methylpiperidinium iodide melted at 204°C. ¹H-NMR (300 MHz, CDCl₃) δ 1.00 (d, 3H), 1.02 (t, 3H), 1.48 (m, 2H),1.82 (m, 2H), 2.10 (m, 5H), 3.28 (s, 3H), 3.60 (m, 2H), 3.70 (m, 4H).

A slight excess of lithium bis[(trifluoromethyl)sulfonyl]imide dissolvedin water was added to an aqueous solution of form1-butyl-1-methyl-3-methylpiperidinium iodide and stirred at roomtemperature for approximately 5 hours. The reaction mixture wastransferred to a separating funnel and the heavy layer washed severaltimes with water. The addition of a small amount of dichloromethaneaided the separation of the aqueous and organic layer. The heavy organiclayer was then evaporated to dryness leaving a pale yellow liquid, form1-butyl-1-methyl-3-methylpiperidiniumbis[(trifluoromethyl)sulfonyl]imide. ES/MS 170 (Cation C₁₁H₂₄N), −280(Anion C₂F₆NS₂O₄).

Example 4

1-butyl-1-methyl-3-methylpiperidinium iodide was formed according toexample 3.

A slight excess of silver dicyanamide (freshly prepared from AgO andNaN(CN)₂) was added to an aqueous solution of1-butyl-1-methyl-3-methylpiperidinium iodide and stirred at roomtemperature for approximately 5 hours. The reaction mixture was filteredand the filtrate evaporated to dryness leaving a clear liquid,1-butyl-1-methyl-3-methylpiperidinium dicyanamide. ES/MS 170 (CationC₁₁H₂₄N), −66 (Anion C₂N₃).

Example 5

A slight excess of 1,5-dibromopentane was added dropwise to a solutionof azepane and sodium hydroxide in water and stirred at reflux forseveral hours. The solution was then cooled to room temperature anddiluted with aqueous sodium hydroxide. The reaction mixture was thenextracted with chloroform, washed with water several times andevaporated to dryness to yield the white solid6-azonia-spiro[5,6]dodecane bromide with a melting point of 260° C.¹H-NMR (300 MHz, D₂O) δ 1.50 (m, 6H, CH₂), 1.75 (m, 8H, CH₂), 3.20 (t,4H, N—CH₂), 3.30 (t, 4H, N—CH₂).

A slight excess of lithium bis[(trifluoromethyl)sulfonyl]imide dissolvedin water was added to an aqueous solution of 6-azonia-spiro[5,6]dodecanebromide and stirred at room temperature for several hours. The reactionmixture was transferred to a separating funnel and the heavy layerwashed several times with water. The addition of a small amount ofdichloromethane aided the separation of the aqueous and organic layer.The heavy organic layer was then evaporated to dryness leaving a paleyellow solid, 6-azonia-spiro[5,6]dodecanebis[(trifluoromethyl)sulfonyl]imide with a melting point of 96° C. ES/MS168 (Cation C₁₁H₂₂N), −280 (Anion C₂F₆NS₂O₄).

Example 6

6-azonia-spiro[5,6]dodecane bromide was formed according to example 5.

A slight excess of silver dicyanamide (freshly prepared from AgO andNaN(CN)₂) was added to an aqueous solution of6-azonia-spiro[5,6]dodecane bromide and stirred at room temperature forseveral hours. The reaction mixture was filtered and the filtrateevaporated to dryness leaving a white solid, 6-azonia-spiro[5,6]dodecanedicyanamide with a melting point of 148° C. ES/MS 168 (Cation C₁₁H₂₂N),−66 (Anion C₂N₃).

Example 7

Hexanedinitrile was hydrogenated in the presence of hydrogen gas and aniron catalyst at an elevated temperature of 140° C. and an elevatedpressure of 4500 psig. Following the hydrogenation, the by-productazapane was separated from the main reaction product 1,6-hexanediamineby distillation at reduced pressure and elevated temperature.

The azepane by-product was then used to form ionic liquids of thepresent invention, for example by the processes in examples 1, 2, 5 and6.

Example 8

2-methylpentanedinitrile was hydrogenated in the presence of hydrogengas and a Raney cobalt catalyst at elevated temperatures of 115° C. andan elevated pressure of 800 psig. Following the hydrogenation, theby-product 3-methylpiperidine was separated from the main reactionproduct 2-methyl-1,5-pentanediamine by distillation at reduced pressureand elevated temperature.

The azepane by-product was then used to form ionic liquids of thepresent invention, for example by the processes in examples 3 and 4.

1. An ionic liquid comprising a cation according to Formula I:

wherein: n is 2, R¹ is selected from the group consisting of: H, C₁-C₁₂alkyl, aryl or together with R² may form a heterocyclic ring, and R² isselected from the group consisting of: H, C₁-C₁₂ alkyl, aryl or togetherwith R¹ may form a heterocyclic ring, and R³ is selected from the groupconsisting of hydrogen and C₁-C₁₂ alkyl, and wherein R¹ and R² are notsimultaneously selected from hydrogen; and an anion, wherein the anionis dicyanamide.
 2. The ionic liquid according to claim 1, wherein R³ ishydrogen.
 3. The ionic liquid according to claim 1, wherein R¹ is amethyl group.
 4. The ionic liquid according to any one of claim 1, 2 or3, wherein R² is a butyl group.
 5. The ionic liquid according to any oneof claim 1, 2 or 3, which is 1-butyl-1-methyl-azepanium dicyanamide. 6.The ionic liquid according to any one of claim 1, 2 or 3, which is6-azonia-spiro[5,6]dodecane dicyanamide.
 7. The ionic liquid accordingto claim 4 which is 1-butyl-1-methyl-azepanium dicyanamide.
 8. The ionicliquid according to claim 4, which is 6-azonia-spiro[5,6]dodecanedicyanamide.